The correct answer is: A. a, the
The word "a" is used before a noun that is not specific. In this case, the speaker is not referring to a particular tall man, but rather to any tall man. The word "the" is used before a noun that is specific. In this case, the speaker is referring to a particular tall man, who has dark hair.
The other options are incorrect because they do not use the correct articles. Option B uses "a" before the noun "dark hair," but "dark hair" is not a specific noun. Option C uses "the" before the noun "tall man," but "tall man" is not a specific noun. Option D uses no articles before either noun, but both nouns are specific.
